Communications systems are known and over time many of these systems and constituent equipment have evolved from analog to digital systems. In digital systems information or traffic in digital form is used to modulate a radio frequency carrier that is used for transmission or transport of the information or traffic. Voice or analog information is converted to and from a digital form using vocoders prior to transmission. Using these approaches enables more services to more users with the same or less bandwidth and at lower costs.
Many presently deployed or legacy systems are largely devoted to voice traffic and many systems that are and are being deployed use a voice channel with a corresponding unique air interface for voice traffic and a separate data channel and corresponding air interface for data traffic. A wireless communications unit, such as some legacy units only support voice channels or only a voice channel or data channel at any one time. The marketplace is beginning to express a need for data transport of small amounts of data at the same time as a voice channel or circuit is maintained. Clearly a need exists for a method and apparatus for transferring data over a voice channel, preferably in a fashion that is transparent to legacy units.